Interactions of cells of the immune system with components of the extracellular matrix (ECM) are responsible for the induction of various immune responses including inflammatory responses. In addition to being an important component of the extracellular structure, the ECM also is involved in cellular signal transduction events by interactions with cellular receptors. Thus, the ECM modulates cell adhesion, cell proliferation, cell differentiation, etc. (Schubert et al. Trends Cell. Biol., 2:63-66, 1992). Major constituents of the ECM include glycosaminoglycans, fibronectin, laminin, collagens, and proteoglycans, which bind specific cell surface receptors via protein—protein and protein-carbohydrate interactions. The glycosaminoglycans are linear polymers of repeating disaccharides often bound covalently to a protein core.
Hyaluronan (also known as hyaluronic acid or hyaluronate) (HA), is a glycosaminoglycan lacking a protein core, and is one of the major non-structural elements of the extracellular matrix (Laurent et al., F.A.S.E.B. J. 6: 2397-2404, 1992; Aruffo et al. Cell. 61:1303-1313, 1990; Culty et al., J. Cell. Biol. 111:2765 1990; Underhill et al. Cell. Sci. 103, 293-298, 1992; Toole et al. Plenum Press, New York, 1384-1386,1991). HA also is expressed on cell surfaces and has been shown to bind several different molecules, including CD44 (Aruffo et al. Cell. 61:1303-1313, 1990; Miyake et al. J. Exp. Med. 172:69-75, 1990), the receptor for HA-mediated motility (RHAMM) (Hardwick et al. J. Cell. Biol 117:1343-1350, 1992), link protein (Hardingham et al. Biochem. J. 177:237-247, 1979), aggrecan (Watanabe et al. J. Biol. Chem. 272:28057-28065, 1997), versican (LeBaron et al. J. Biol. Chem. 267:10003-10010, 1992), hyaluronectin (Delpech et al. J. Neurochem. 36:855-859, 1981), neurocan (Rauch et al. J. Biol. Chem., 267:19536-19547, 1992), liver sinusoidal endothelial HA receptor, inter-α-trypsin inhibitor-related proteins (10), BEHAB (brain-enriched HA binding), CD38, lymphatic vessel endothelial HA receptor 1, and white fat/bone marrow/osteoblast HA binding proteins. Conversely, CD44 binds not only HA, but also collagens, fibronectin, chondroitin sulfates, heparin, heparin sulfate, and serglycins. Thus, although CD44 (or HA) is generally considered to be a primary HA receptor (or a principal CD44 ligand), HA-CD44 interaction represents one of the multiple mechanisms by which HA and CD44 may regulate cellular activities.
HA is a repeating disaccharide of [GlcNAcβ1-4GlcUAβ1-3]n that exists in vivo as a high molecular weight linear polysaccharide. HA is found in mammals predominantly in connective tissues, skin, cartilage, and in synovial fluid, and is also the main constituent of the vitreous of the eye. In connective tissue, the water of hydration associated with HA creates spaces between tissues, thus creating an environment conducive to cell movement and proliferation. HA plays a key role in biological phenomena associated with cell motility including rapid development, regeneration, repair, embryogenesis, embryological development, wound healing, angiogenesis, and tumorigenesis (Toole et al. Plenum Press, New York, 1384-1386,1991; Bertrand et al. Int. J. Cancer. 52:1-6, 1992; Knudson et al. F.A.S.E.B. J. 7:1233-1241, 1993). HA levels have been shown to correlate with tumor aggressiveness (Ozello et al. Cancer. Res. 20:600-604, 1960; Takeuchi et al. Cancer. Res. 36:2133-2139, 1976; Kimata et al. Cancer. Res. 43:1347-1354, 1983), and can be indicative of the invasive properties of tumor cells (Knupfer et al. Anticancer. Res. 18:353-6, 1998).
HA also is involved in immune responses, for example, increased binding of HA to one of its receptors, CD44, has been shown to mediate the primary adhesion (“rolling”) of lymphocytes to vascular endothelial cells under conditions of physiologic shear stress, and this interaction mediates activated T cell extravasation into an inflamed site in vivo in mice (DeGrendele et al. J. Exp. Med. 183:1119-1130, 1996; DeGrendele et al., J. Immunol. 159:2549-2553, 1997; DeGrendele, et al., Science. 278:672-675, 1997b). Alterations in levels of HA and other glycosaminoglycans have also been associated with unwanted immune responses, and in diseases and disorders such as rheumatoid arthritis, atopic dermatitis, psoriasis, multiple sclerosis, transplantation rejection. For example, HA and other glycosaminoglycans display are altered in autoimmune disorders such as arthritis, and decreased levels of both hyaluronic acid and chondroitin 6-sulfate have been found in the diseased synovial fluid of both adults with rheumatoid arthritis (Bensouyad et al. Ann. Rheum. Dis. 49:301-307, 1990) and children with juvenile rheumatoid arthritis (Spelling et al. Clin. Exp.Rheumatol. 9:195-9, 1991).
Dendritic cells (DC) play essential roles in the induction of cellular immune responses to a variety of relevant antigens. DC are known to play critical roles in the induction of cellular immune responses against a wide variety of antigens of relevance, including chemical haptens, foreign proteins, infectious microbes, and tumor-associated antigens (Steinman et al. Ann. Rev. Immunol. 9:271, 1991; Stingl et al. ed. McGraw Hill and Co. New York, p. 172, 1993). Interaction between HA, expressed on endothelial cells, and CD44, expressed on activated dendritic cells as well as T cells, and granulocytes, is believed to mediate homing of such leukocytes to their target sites.
Glycosaminoglycans, particularly HA, also are known to mediate other cellular interactions that involve binding and entry into a cell. For example, HA is involved in infection of mammalian cells by the Human Immunodeficiency Virus (HIV), since HIV is known to bind to HA upon infection. Both HA and monoclonal antibodies to its receptor CD44 were found to inhibit HIV infection of monocytes by monocytotropic HIV (Levesque et al. J. Immunol. 156:1557-65, 1996). HA also is involved in mammalian zygote formation by mediating binding of the oocyte and the sperm. Data indicate that HA in the cumulus matrix may act to prime the fertilizing sperm for induction of the acrosome reaction by constituents of the cumulus and/or zona pellucida. HA is thought to mediate this interaction by binding to the PH-20 protein to increase basal levels of intracellular calcium and thereby potentiate the acrosome reaction (Sabeur et al. Zygote. 6:103-11, 1998). HA mediates sperm motility by enhancing phosphorylation of proteins including HA binding protein (Ranganathan et al. Cell. Mol. Biol. Res. 41:467-76, 1995).
Other important glycosaminoglycans involved in a variety of physiological and pathological states include, chondroitin sulfate A, chondroitin sulfate C, dermatan sulfate, heparin, keratan sulfate, keratosulfate, chitin, chitosan 1, and chitosan 2. These and other glycosaminoglycans, and particularly hyaluronic acid, play important roles in such varying physiological processes make them attractive targets for therapeutic agents. However, glycosaminoglyeans have been found to be nearly non-antigenic, and hence, very few antibodies that recognize glycosaminoglycans have been isolated. Due to the lack of antigenicity, it has been technically difficult to develop inhibitors or probes of glycosaminoglycans. As such, there is a need in the art for inhibitors of glycosaminoglycan-mediated processes, and in particular for inhibitors of hyaluronic acid-mediated processes.